H1N1 virus widely seen to be tailing off

Mateo Munsayac, 9, received a swine flu vaccination from Merlita Layug yesterday at a county public health center. San Diego County continues to provide free doses of H1N1 vaccine at community clinics and at public events such as swap meets.
— K.C. Alfred / Union-Tribune

Mateo Munsayac, 9, received a swine flu vaccination from Merlita Layug yesterday at a county public health center. San Diego County continues to provide free doses of H1N1 vaccine at community clinics and at public events such as swap meets.
— K.C. Alfred / Union-Tribune

SWINE FLU’S IMPACT

Worldwide infections: 213 countries have reported H1N1 cases since the pandemic began last April

U.S. infections: 59 million

Deaths: 16,713 estimated worldwide, roughly 12,000 in the United States and 55 in San Diego County

U.S. hospitalizations: 265,000

U.S. vaccinations: 95 million doses administered, with more than 30 million remaining

Sources: U.S. Centers for Disease Control and Prevention; World Health Organization; San Diego County Health and Human Services Agency

In the latest sign that the second wave of swine flu has largely ended, no new infections were reported in the county’s most recent weekly survey of influenza activity in the region.

That marked the first local break in the global pandemic since the first two cases of the disease, also called H1N1 influenza A, were discovered in San Diego County nearly a year ago.

On Monday, officials at Sharp HealthCare’s five hospitals will drop restrictions for visiting patients, including an age limit for visitors, that were put in place when the pandemic emerged.

Updates yesterday from across the country and around the world were equally encouraging.

No states reported widespread influenza activity for the week ending March 6, and 33 states — including California — reported sporadic instances of laboratory-confirmed cases, according to the federal Centers for Disease Control and Prevention.

The virus appears to be most prevalent and spreading in West Africa and Southeast Asia, but increasingly scarce in other regions, the World Health Organization said.

While concerns that swine flu might mount another assault this spring in the United States have waned in recent weeks, public-health officials remain cautious because the H1N1 virus’ behavior is unpredictable.

College students heading to spring break and crowding together for parties could allow swine flu to re-establish itself, said Dr. Wilma Wooten, the county’s public health officer.

“It’s certainly possible that we could create clusters of infection,” she said. “That’s why we are (still) trying to vigorously vaccinate people.”

To that end, the county continues to provide free doses of H1N1 vaccine at community clinics and at public events such as swap meets.

The pandemic has failed to live up to the doomsday scenarios evoked during the earliest days of the crisis, when the virus crippled Mexico for two weeks, prompted temporary school closures in San Diego County and other parts of the United States, and quickly spread around the world.

Based on the latest CDC estimates, the virus killed about four of every 100,000 people in the United States, said Dr. James Chin, who recently retired from his job as a professor of epidemiology at the University of California Berkeley. That’s far below the 2,500 deaths per 100,000 people worldwide recorded during the 1918 influenza pandemic, and it’s less than the 10 U.S. deaths per 100,000 people that occur each year from seasonal flu.

The biggest factor that drove the anxious response to swine flu by government leaders, the media and the public was the virus’ severe and sometimes lethal effect on young and otherwise healthy people, Chin said. In contrast, strains of seasonal flu usually level their hardest hits on the elderly.

In retrospect, some people criticize the CDC and WHO for responding aggressively to the pandemic before it became clear how virulent the disease would be.

Such second-guessing is inevitable given the varied paths that viruses take, Chin said.

“You have to prepare for the worst.” he said. “That’s what they did. They prepared for the worst and hoped for the best, and the best came.”

Physicians and public-health officials learned lessons from the experience, said Dr. Gonzalo Ballon-Landa, an infectious-disease specialist affiliated with Scripps Mercy Hospital in San Diego. He also heads the local Group to Eradicate Resistant Microorganisms.

“This has been a wonderful dress rehearsal,” he said.

Ballon-Landa praised medical providers for embracing their duties during the pandemic and largely heeding calls to be vaccinated.

“We didn’t have a health-care worker revolt. We didn’t have people saying, ‘I’m not going to take care of sick people because I don’t want to bring it to my children,’ ” he said.

Despite intensive efforts to inoculate nearly half of the U.S. population, interest in the vaccine waned after the outbreak peaked in late October and early November.

At least 30 million doses of the vaccine remain, said CDC spokesman Richard Quartarone.

The number tops 80,000 in San Diego County, Wooten said.

Unused shots will be replaced in the fall by a single flu vaccine that will combine dead versions of the H1N1, influenza A H3N2 and influenza B viruses. Drug companies have begun making the new shots, which take several months to develop and should be available by early October.

In case the manufacturing process hits an unexpected snag, CDC officials are asking health providers to hang on to leftover H1N1 doses at least until 2011 as a backup.

“I am delighted they are recommending that,” said Ballon-Landa, who had 100 H1N1 shots stored in a refrigerator at his office yesterday. “It could be that in the fall we have this thing come back.”

A more immediate threat could come from common flu strains, which have been practically nonexistent during the current flu season.

Scientists don’t understand why some influenza viruses squeeze others out and become dominant from time to time. When the most widespread virus fades, other versions can rush in to fill the void.

CDC epidemiologists are monitoring tests of people with flu-like symptoms for any sign of such a turn, Quartarone said.

Indeed, the WHO yesterday reported recent surges in seasonal influenza B infections in China, Mongolia, Iran, Russia and Sweden. The agency warned that the viral outbreak appears to be gaining momentum and moving west to Europe.